This invention relates to a new process for the production of 4-amino-2,2,6,6-tetramethyl-piperidine by the reductive amination of phorone.
It is already known that 4-amino-2,2,6,6-tetramethyl piperidine can be obtained in accordance with the following reaction scheme: ##SPC1##
Phorone (I) is condensed with ammonia to form 2,2,6,6-tetramethyl-4-piperidone ["triacetone amine"](II), cf. Pharm. Chem. J. 1971, page 44 and Bull. Soc. chim. France 1958, pages 345 to 346. The triacetone amine is then reacted with hydroxylamine to form the oxime (III) (cf. Berichte der Deutschen Chemischen Gesellschaft, vol. 29, page 53 (1896) and Bull Soc. chim. France 1965, page 3282), from which the 4-amino-2,2,6,6-tetramethyl piperidine (IV) is obtained by reduction with zinc/hydrochloric acid or metallic sodium in amyl alcohol (cf. Liebigs Ann. d. Chemie, vol. 417, pages 118 to 119 (1918) and Izv. Akad. Nauk. SSSR Ser. Khim. 1966, page 1477).
Unfortunately, the total yield of this synthesis which involves 3 steps only amounts to about 30%, and furthermore a number of byproducts are inevitably formed. Accordingly, there is a considerable need for a commercially favourable process for the production of 4-amino-2,2,6,6-tetramethyl piperidine.